The Red Rocks Fitness Challenge starts with a free session on May 17 and invites participants of all ages and fitness levels to challenge themselves in the natural surroundings of Red Rocks Amphitheatre.

May 17-18: The 9 a.m. May 17 Bellco Colfax 5K is a kick-off for the ninth annual Kaiser Permanente Colfax Marathon (May 18, details on the website) and includes two starts, one for runners and one for families, dogs and wheels. Post-race festivities include live music, a photo booth, awards and entertainment. $37, $20 children 12 and under and seniors 65+, $20 for athletes with disabilities. Denver’s City Park, runcolfax.org

The Boulder Fringe

May 26: Presents “Running for the Fringe” and inviting walkers and runners to join the Boulder Fringe Festival’s Fringe Team for the BolderBoulder and to wear their finest fringe. Boulder, 303-803-5643, boulderfringe.com

Denver Century Ride

June 14: The fifth annual Coldwell Banker Denver Century Ride encourages cyclists of all levels to “Explore, Discover and Experience.” Course options include the Full Century, 3/4 Century, 1/2 Century and 1/4 Century. The start and finish and Post Ride Street Party is on Main Street at The Shops at Northfield Stapleton, 8340 Northfield Blvd. Children are invited to decorate their bikes for the Denver Century Ride Kids Bicycle Parade. denvercenturyride.com

May 18: The 2014 Walk to Cure Arthritis is a benefit to raise awareness and funds to prevent, control and cure arthritis that affects 52 million adults and 300,000 children. A 5K, three-mile and one-mile course is included. This year’s National Youth Honoree is 12-year-old Claire Brennan who was diagnosed with juvenile rheumatoid arthritis at age 2. Dogs are welcome. Post-walk festivities include a Kids Zone, entertainment, refreshments, prizes and awards. Washington Park, 701 S. Franklin St., denverarthritiswalk.org

June 1: The Colorado Columbines Women’s Running Club presents the annual race offering an 8-mile run starting at 8 a.m. and a 4-mile at 8:30 a.m. A Sprouts Kids’ Fun Run and a post-race festival is included. The cost is $40 for the 8-mile and $35 for the 4-mile race, discounts available. Prizes will be awarded. Proceeds benefit the Women’s Bean Project, a nonprofit that teaches life and job skills to women in need. Park entry fees will be waived. Aurora Reservoir, 5800 S. Powhaton Road, Aurora, columbineclassic.org

June 21-25: “5 Days — 50 States — 550 Runners” is the theme of the annual relay inviting individuals and teams to participate in all 50 states simultaneously. Proceeds benefit cancer survivors and their families through the LiveStrong Foundation and Camp Keseum. Visit the website for more information. 550relay.com

May 24-25: New Belgium Brewing sponsors this annual benefit for Gunnison Trails, a nonprofit that maintains Gunnison’s biking trails. Remaining race options include the 64-mile Full Growler beginning at 7 a.m. May 25, this race is recommended for experienced mountain bikers; and The Late Bus 32 at 7 a.m. May 25. The 32-mile Half-Growler on May 24 is closed for registration. Gunnison, bikereg.com/21978

Insane Inflatable 5K

May 31: The national race tour of 16 cities across the United States is coming to Dick’s Sporting Good Park. The course, open to ages 14 and older, is approximately three miles and features 12 obstacles ranging in size and complexity. A Junior Bouncers course is set up for ages 7-13. Music, refreshments, vendors and other inflatables are included. $75 event-day registration, $49 in advance. $15 for Junior Bouncers. A portion of the proceeds will be donated to local nonprofits. 6000 Victory Way, Commerce City, insaneinflatable5k.com

Lucky Mutt Strut 5K

June 7: Annual benefit for the MaxFund Animal Adoption Center. 7:30-8:45 a.m. check-in/registration, 9 a.m. start for runners, 9:15 a.m. start for walkers. The cost is $30 adults, $20 children under 12, in advance; $35 on race day. A Lazy Dogz and Sleepy Catz $30 fee to stay in bed and still support the no-kill shelter that cares for more than 1,000 animals per year. Dogs are welcome. Cheesman Park, 1599 E. 8th Ave., 303-547-6195, maxfund.org

NAMIWalks 2014

May 17: A benefit for the National Alliance on Mental Health. 8 a.m. registration, 9:30 a.m. walk begins. There is no registration fee, participants are encouraged to collect donations. A walk is also offered in Grand Junction. Centennial Center Park, 13050 E. Peakview, Centennial, namiwalks.org

June 7: The annual 55-mile bike ride to benefit Parkinson’s Disease Research and The Michael J. Fox Foundation for Parkinson’s Research. Activities include the ride, information on Parkinson’s Disease, a guest speaker, tech support from Performance Bicycle and Campus Cycles, a free lunch, live music and a beer garden. The race begins and ends at Glendale’s Creekside Park located at South Clermont Street and East Virginia Avenue, 888-548-3002, pedalingforparkinsons.org

Roxborough State Park Moonlight Hike

May 13: Family-friendly hike led by a volunteer naturalist. Start time is 7 p.m. $7.50 each or $24 family rate (two adults and two children ages 6-12). Children must be accompanied by an adult. Proceeds from the hike benefit educational programs. Reservations required. Upcoming hikes: June 12, July 11, Aug. 9, Sept. 8 and Oct. 7. 4751 E. Roxborough Drive, Roxborough, 303-973-3959

Sudan Freedom Walk

May 31: The fourth annual walk to free Sudanese citizens trapped in North Sudan and return them to home to South Sudan. 9 a.m. registration, 9:30 a.m. opening ceremony and speakers, 10 a.m. walk begins. There is a $7 per vehicle entry fee into the park. Bear Creek Lake Park, 15600 W. Morrison Road, Lakewood, FreeForFifty.com

T21 Fun Run and 5K

June 7: The Down Syndrome — Autism Connection presents the inaugural benefit supporting programs and services for those of all ages impacted by Down syndrome and Autism (DS-ASD). Sign up for the 5K, Fun Run or as a virtual walker. Participants are invited to set up their own online team fundraising page. Check in is at 7 a.m. at Road Runner Sports Westminster in the Shops at Walnut Creek, 10436 Town Center Drive, Westminster. Race time is 8 a.m. Prizes included. 720-309-5825, roadrunnersports.fundly.com/t21funrunand5k, ds-asd-connection.org/

May 17-July 12: Denver Parks & Recreation and Red Rocks Amphitheatre presents the fourth annual fitness program open to all ages and abilities. A team of certified trainers and a lifestyle coach host group sessions inside the amphitheatre and offer nutrition advice, 7-8 a.m. Saturdays (there is no workout July 5). Youth programming is offered on select dates. A season pass is $70 and includes all eight sessions, a t-shirt and goodie bag. A package of five sessions is $40, the drop-in rate is $12. The May 17 session is free. Visit the website for details. redrocksfitnesschallenge.com

ONGOING

Feisty Fit Females

A free exercise group for female cancer survivors meets the final Thursday of each month, 6:30-8:30 p.m. 303-798-7614, feistyfitfemales.org

Rocky Mountain National Park

Visit the website for trail descriptions, pictures, maps and more on more than 70 hiking trails in the 265,000-acre park. Search by location, trail features, difficulty level or alphabetically by trail name. rockymountainhikingtrails.com